Need your thoughts! screens

So the time has come for me to upgrade my system.
But im getting caught up on whether i upgrade my screens.
I currently run 2 27" bq 60hz monitors and im tossing up switching one out for a new 144hz bq 27"
my questions are:
1. does 144hz make a big enough difference to upgrade to if your screens are still working fine.
2. say i am upgrading my screen is there a point to go 4k or stick with 1080.

FPS > Quality every time. 144hz vs 60fps is much more noticable, feels much more responsive and smooth.

You would probably want to stick with 1080p as this will pretty much always net you a stable ~144fps (depending on your card). If you have a monster GPU setup, you could even consider some of those new 1440p 144hz monitors. I have a 1440p monitor, and I quite like it vs my old 1080p one, however, the difference isn't so large that I couldn't go back to 1080p.